Claudication, defined as walking-induced leg discomfort and gait dysfunction relieved by rest, affects 5% of Americans over 55 years of age. Claudicating patients adopt sedentary lifestyles and cluster at the extreme low end of the physical activity spectrum, escalating risk for adverse health effects. The primary therapeutic goals for claudicating patients are restoration of leg function and prevention of disease progression. Current, rehabilitative interventions focus on inadequate blood flow as the only cause of claudication. Operative revascularization and/or exercise therapy are the principal conventional therapeutic modalities, providing only modest rehabilitative benefit. Applying biomechanical analysis to gait of claudicating patients, our team has developed preliminary data indicating that blood flow is not the only mechanism producing the limb dysfunction of claudication. Several laboratories including our own have demonstrated a myopathy, characterized by mitochondrial dysfunction, oxidative damage and inflammation, in leg skeletal muscle of claudicating patients. These conditions have not been quantified, comprehensively, in relation to claudication, and their association with severity of claudication is not known. Our hypothesis is that blood flow restriction is not a good predictor of limb dysfunction in claudication, whereas muscle mitochondrial dysfunction, oxidative damage and inflammation are strong predictors of limb dysfunction both at baseline and after conventional therapy with revascularization or supervised exercise. Under Aim #1, we will acquire precise measurements of gastrocnemius mitochondrial function, oxidative damage and inflammation in claudicating patients, at the time of their initial presentation, and evaluate these measurements as predictors of objective measures of limb function and subjective measures of quality of life. Under Aims #2 and #3, we will evaluate the effects of revascularization (Aim#2) and supervised exercise therapy (Aim#3) on mitochondrial dysfunction, oxidative damage and inflammation in claudicating gastrocnemius and on objective measures of limb function and subjective measures of quality of life. If our hypothesis is correct, the work in Aim #2 will for the first time definitively demonstrate that blood flow restriction due to blockages in the arterial tree is not the only cause of claudication. The work under Aims #2 and #3 will determine whether revascularization or exercise therapy has a beneficial effect on the myopathy of claudicating muscle with associated improvement in limb function and quality of life. Finally, the proposed studies under Aims #1, #2 and #3 will provide quantitative modeling of a panel of mechanistic (bioenergetics, oxidative stress and inflammation) parameters as predictors of objective measurements of claudicating limb function and subjective measures of quality of life commonly used for clinical assessment. Measurements of gastrocnemius mitochondrial function, oxidative damage and inflammation may be useful tools that permit staging of disease for optimum intervention and evaluation of therapeutic interventions that specifically target these conditions, improving rehabilitative outcomes.